TNF-alpha- and TRAIL-resistant glioma cells undergo autophagy-dependent cell death induced by activated microglia.
The role of microglia, the brain resident macrophages, in glioma biology is still ill-defined. Despite their cytotoxic potential, these cells that significantly infiltrate the tumor mass seem to support tumor growth rather than tumor eradication. A proper activation of microglia anti-tumor activities within the tumor may provide a valuable additional arm of defense to immunotherapies against brain tumors. We herewith report a detailed characterization of (lipopolysaccharide and interferon-gamma)-induced anti-tumor activities of mouse primary microglia towards two TNF-alpha and TRAIL resistant glioma cell lines, in cell monolayer or spheroid cultures and in collagen-embedded tumor explants. Irrespective of the mouse strain, stimulated microglia secreted proteic factors that decreased proliferation and migration of these glioma cells and efficiently killed them. Death occurred specifically in glioma cells as demonstrated by the lack of toxicity of microglia supernatant towards primary cultures of astrocytes or neurons. Cell death was characterized by the early accumulation of acidic vesicles, phosphatidylserine exposure, appearance of double-membrane cytoplasmic vesicles, extensive zeiosis and a very late loss of DNA in cells that had lost membrane integrity. Inhibition of autophagosome formation efficiently protected glioma cells from death whereas caspase inhibition could only prevent DNA loss but not cytotoxicity. Death however, resulted from a blockade by microglia supernatant of the basal autophagic flux present in the glioma cells. These observations demonstrate that glioma cells resistant to apoptotic death ligands could be successfully and specifically killed through autophagy-dependent death induced by appropriately activated microglia.
Mora
Rodrigo
R
INSERM U701, German Cancer Research Centre, Program Infection and Cancer, Heidelberg, Germany.
Abschuetz
Anette
A
Kees
Tim
T
Dokic
Ivana
I
Joschko
Natalie
N
Kleber
Susanne
S
Geibig
Renate
R
Mosconi
Eric
E
Zentgraf
Hanswalter
H
Martin-Villalba
Ana
A
Régnier-Vigouroux
Anne
A
D000818:Animals; D001343:Autophagy; D061945:Caspase Inhibitors; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002478:Cells, Cultured; D003094:Collagen; D004247:DNA / Q000378:metabolism; D005910:Glioma / Q000473:pathology* / Q000503:physiopathology; D066298:In Vitro Techniques; D007371:Interferon-gamma / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D017628:Microglia / Q000502:physiology*; D009569:Nitric Oxide / Q000378:metabolism; D009842:Oligopeptides / Q000378:metabolism; D010718:Phosphatidylserines / Q000378:metabolism; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
D061945:Caspase Inhibitors; D008070:Lipopolysaccharides; D009842:Oligopeptides; D010718:Phosphatidylserines; D053221:TNF-Related Apoptosis-Inducing Ligand; C505654:Tnfsf10 protein, mouse; D014409:Tumor Necrosis Factor-alpha; C517629:benzyloxycarbonyl-valyl-alanyl-aspartic acid; D009569:Nitric Oxide; D007371:Interferon-gamma; D003094:Collagen; D004247:DNA